This invention relates to a stop ring used for an optical connector that located between optical fiber transmission lines in order for transmission line switching or cutting off, parts used for fixing an optical fiber cord.
In the conventional optical connector, an optical fiber cord is fixed by caulking compression and friction with a strength member sandwiched between an outer periphery of an opposite end of a stop ring holding a ferrule through a compression spring to a side connecting the ferrule and a ring-formed caulking ring A. Furthermore, an outer jacket of the optical fiber cord is also fixed by crimping from a rear of the caulking ring A by another caulking ring A. Refer to Japanese Industrial standard JIS 5973.
As another method, as shown in FIG. 3 there has been a method of fixing with a heat-shrinkable tube 50 after arranging the strength member 40 at an outer periphery of a stop ring 10 after inserting a buffer coating 30 on a side of the stop ring 10 fixing a cord 20.
Because the conventional optical connector requires a caulking tool and further two metal-make caulking rings, there has been a problem that two caulking processes are required complicating the processes and raising fabrication cost. Furthermore, the caulking ring is required to have even pressure and friction to the optical fiber cord. There has been a problem of high forming accuracy requirement and increase in parts fabrication cost.
Also, in the method of using a heat-shrinkable tube, there has been a problem that the optical fiber cord is easily removed because the heat-shrinkable tube is low in compression fixing strength.
Further in recent year, the optical connector needs down sizing and a diameter of the optical fiber cord becomes smaller. Then the number of strength member is decrease and there has been a problem that the connecting strength by caulking ring is decrease. Furthermore because of small-diameter cord, a radius of curvature during folding the strength member becomes small and the strength member tends to break.
The present invention has an adhesive and heat-shrinkable tube on an optical fiber cord fixing side of the stop ring, i.e., on an outer periphery of an opposite end connecting a spring urging a ferrule, and a surface of an outer sheath of an optical fiber cord at an end connecting the stop ring, and is arranged with a strength member in the adhesive at between an outer periphery of the stop ring and the heat-shrinkable tube. By thus using both the adhesive and the heat-shrinkable tube, a plurality of caulking rings are unnecessary that are a cause of process increase, enabling the reduction in the number of parts and manufacture cost.
Also, in the present invention, by using the heat-shrinkable tube with adhesive that an adhesive is previously applied to an inner surface of the heat-shrinkable tube, it is possible to collectively fix the strength member and the outer sheath to the stop ring through once heating.
Furthermore, in the present invention, a cut-out on the optical fiber cord fixing end side of the stop ring and a through-hole coupled to the cut-out in an outer peripheral surface nearby the end surface are provided, and the strength member is passed through the through-hole. Furthermore, the strength member passing the through-hole is bent to an opposite side of the end of the stop ring. The heat-shrinkable tube is arranged in a manner covering the fixing end of the optical fiber cord of the stop ring and the outer jacket of the optical cord having at a surface the bent strength member. By heating, the stop ring and the optical fiber cord are fixed.
With the above structure, the optical fiber cord can be firmly fixed with respect to a tensile direction due to a tensile strength of the strength member. Furthermore, by the adhesive, it is possible to prevent against removal of the strength member and increase the air-tightness between the heat-shrinkable tube and optical cord outer sheath. It is possible to prevent moisture from entering to an inside of the connector. It is possible to obtain a connector excellent in environmental reliability.
Also, in the present invention, the stop ring further comprising a claw which project in the direction of the radius of the stop ring. Then the claw limits a movement of heat-shrinkable tube in the axis direction and the claw prevent the tube from coming out. As a consequent, the fixing strength of an optical connector by strength member is increased.